1. Field of the Invention
The present invention relates to a knitted slide fastener comprising a fastener tape formed by a warp knitting structure and a successive fastener element row being simultaneously knitted into an element attaching portion of a longitudinally side edge portion of the fastener tape, and specifically, to a knitted slide fastener comprising the successive fastener element row firmly attached to the element attaching portion having a fine knitting structure, wherein there is no irregularity of pitches between or separation of elements of the element row, and stability in a shape of the fastener element attaching portion of the fastener tape is ensured.
2. Description of the Related Art
Conventionally, as a knitted slide fastener of the type in which a continuous fastener element row is knitted simultaneously with knitting of a fastener tape, there is a known knitted slide fastener as disclosed in U.S. Pat. No. 3,864,945 and Japanese Patent Laid-open Publication No. 2-255104, for example, in which a continuous fastener element row made of plastic monofilament is mounted and fixed by being knitted into stitches of a plurality of fixing chain stitch yarns simultaneously with knitting of the fastener tape. However, in the knitted slide fastener disclosed in the above U.S. patent, because each element of the successive fastener element row is fixed merely by a sinker loop of each fixing chain stitch yarn which extends across an upper face of a leg portion of each the fastener element, and because the foundation structure of the attaching portion is formed by needle loops of the chain stitch yarns and weft in-laid yarns, a fixing force is weak in conjunction with its stretch peculiar to the stitches of the chain stitch. In the knitted slide fastener disclosed in the latter Publication, because the leg portion of each fastener element of the fastener element row are fixed by sinker loop of each fixing chain stitch yarn and the foundation structure at the fastener element attaching portion is consisted of needle loops of the fixing chain stitch yarn and weft in-laid yarns, fixing force of the fastener element row is weak, and the fixing side structure becomes quite coarse, so that a coupled portion of the fastener element rows coupled with each other rises, which is liable to cause separation of the fastener elements from each other, especially when a fastener face receives a pushing up bending stress as shown in FIG. 11. In order to avoid the problem, the fixing knitting yarns can be thicker than other knitting yarns to firmly fix the fastener element row, but distances between knitting needles of a normal warp knitting machine are very small and the knitting needles are required to be fine in order to increase the distances. Therefore, a thickness of the knitting yarns and a number of knitting yarns to be twisted around the knitting needle are naturally limited.
There is a knitted slide fastener developed to solve the above problems as disclosed in Japanese Patent Laid-open Publication No. 8-314, for example. In the knitted slide fastener disclosed in this Publication, another chain stitch yarn is added to a needle loop group constituting a wale on a tape foundation structure side formed by chain stitch threads for fixing the fastener element row. Because of the above chain stitch knitted by overlapping stitches of the foundation structure at the attaching portion of the fastener element row, the attaching portion is made fine, and fixing of the fastener element line is stabilized.
However, in the above knitted slide fastener disclosed in Japanese Patent Laid-open Publication No. 8-314, a knitting yarn for holding the fastener element row from above on a side opposite from the tape foundation structure side still is only sinker loops of the fixing chain stitch yarns. As a result, knitting structures disposed on and under the fastener element row are unbalanced, and a structure on the upper side of the fastener element row is weak. In this case, when the fastener face receives the pushing up bending stress, separation of the fastener elements from each other is liable to be caused. Furthermore, knitting with another chain stitch thread overlapping as disclosed in the above Japanese Patent Laidopen Publication so as to stabilize the stitches themselves of the fixing chain stitch would result that three knitting threads including a thread for tricot stitches are twisted around a knitting needle, thus a strain is put on the knitting needle.